Australia said the search for missing Malaysia Airlines Flight MH370 continued uninterrupted Wednesday, even as the head of the search coordination agency was sent to Ukraine to help with the MH17 tragedy.

Australia leads the multinational search for MH370 which disappeared on March 8 carrying 239 people and is believed to have crashed in the southern Indian Ocean.

It has also been drawn into the latest incident to befall Malaysia Airlines, with 28 nationals and at least nine permanent residents onboard MH17 which was apparently shot down last week in Ukraine.

"The search for missing Malaysia Airlines flight MH370, which disappeared on 8 March on a flight to Beijing from Kuala Lumpur, continues uninterrupted," Deputy Prime Minister Warren Truss said.

"We remain fully committed to conducting a thorough undersea search of the likely impact zone in the Indian Ocean."

On Monday, Prime Minister Tony Abbott appointed retired Air Chief Marshal Angus Houston as his special envoy to lead Australia's efforts on the ground in Ukraine to help recover, identify and repatriate Australians killed in the downing of MH17.

Houston also heads the Joint Agency Coordination Centre (JACC) which coordinates Australia's support for the MH370 search.

Truss said Australia owed it to the families of all of those on board MH370, as well as the travelling public and the wider world, to solve the mystery of what befell the Boeing jet.

"Deputy Coordinator Judith Zielke will oversee the operations of the JACC, ensuring that the public and other stakeholders, particularly the families of those on board, are well informed about the progress of the search," he said.

Despite an extensive air, sea surface and underwater search, no trace of MH370 has ever been found.

Experts are now surveying an area of about 60,000 square kilometres using two vessels, Chinese survey ship Zhu Kezhen and an Australian-contracted vessel, to map the ocean floor, considered crucial for the underwater search.

The Australian Transport Safety Bureau (ATSB), which is coordinating this work, is assessing tenders to engage a contractor to manage this element of the search, Truss said.

"The underwater search is likely to commence in early September and take up to 12 months to complete," he said.

"It will aim to locate the aircraft and any evidence (such as debris and the flight recorders) to assist the Malaysian investigation of the disappearance of MH370."

Australian officials have said MH370 was almost certainly on autopilot when it ran out of fuel and crashed, with the crew likely "unresponsive" due to a lack of oxygen.